Long story short, I was in the gun store the other day talking to an older gentlemen who said that SAAMI lowered the MAP for .357 magnum several decades ago in response to the ultra-lightweight revolvers coming out not being sufficiently sturdy to survive the ammunition.
Is there any truth to this? What year did this change occur? What was the original pressure specification?
"There is no saint without a past, no sinner without a future."
- Saint Augustine
SAAMI Specs on pressure is 45,000 CUP or 35,000 PSI . It has been that for years. NOW, what the factories voluntarily load to as long as it is safe is up to them.
They may load to lower pressures if they desire.
Who knows?
It was the change from CUP to PSI. While there is no 1:1 formula to convert the two, the old 45,000 CUP standard was a significantly higher pressure than today's 35000 PSI. I've heard rumors same as anyone on why the change, but never heard it from the horses mouth. 44 mag is another one that was nerfed, and I don't think too many were wanting that in lightweight guns. As 44mag#1 points out, 45000 CUP is still a recognized standard, it's just that nobody uses a crusher system anymore. Europes CIP standards are very close to the USA CUP standards. They allow 44,000 PSI in 357 mag.
Correct if I am wrong as I am most of the time but doesn't both modes of pressure testing use the same reference ammo?Originally Posted by megasupermagnum
Thank you much!
"There is no saint without a past, no sinner without a future."
- Saint Augustine
I don't know, but I don't see why they couldn't.
I am Confused now... If we were to Measure 45,000 CUP ammo with a PSI transducer... What would the PSI Reading Be???
To me... that would be Apples to Apples....Curiosity gots me Now...
I am all ears on this upcoming answer.
Hodgdon list CUP and PSI on their 357 Mag data.
There is no direct correlation of one reading vs. the other. The current reference ammo is calibrated for psi using the conformal transducer. The only users of radial copper pressure test barrels today may be some powder manufacturers and they would either use older reference ammo calibrated for radial copper or fire a fresh assessment with radial copper using the current reference ammo to determine the correction factor for that one particular lot.
The ENEMY is listening.
HE wants to know what YOU know.
Keep it to yourself.
So would it be a fair assessment to say that the CUP testing method is still used and that would presumptuous to say no one uses the CUP method anymore? Maybe not much use but it still gets used.
And, if the CUP method is referenced along with a PSI method they may be referenced with the same reference ammo that is a given pressure that is within proper tolerances?
Essentially yes. The radial copper test barrel remain in use mostly in the smaller labs and in calibers which don't see a lot of volume. Radial copper test barrels tend to go out of calibration when there is erosion in the piston hole. In lower pressure rounds such as .45 ACP or .38 Special they last a long time. In 9mm or .357 Mag less so. When I was at Ruger in the 1980s during the transition conversion period a radial copper test barrel which no longer shot to reference calibration would sometimes be salvaged by plugging the worn piston hole with a "long" piston, then re-fitting a transducer to the barrel and conducting test firings to see if it produced acceptable results. About half the time you could salvage the barrel for limited experimental work, although it would not hold up to frequent daily use as required for ammunition production. The cost of a new replacement pressure test barrel in the 1980s was about $2000. Probably twice that today, so for limited use the expedient was worthwhile.
Last edited by Outpost75; 04-05-2023 at 11:35 PM.
The ENEMY is listening.
HE wants to know what YOU know.
Keep it to yourself.
I'm sure someone can explain the scientific reasoning why it can't be done exactly. A study was done on a number of cartridges as you suggest, and they did come up with a formula, but be aware it is neither widely accepted or proven to be true. You can read to your hearts content. https://www.shootingsoftware.com/ftp/psicuparticle2.pdf. Just note that European CIP standards are very close to SAMMI CUP standards. We are talking about only the peak pressures, and both CUP and Piezo methods measure peak pressure or max average pressure for our reloading purposes. It's rare though that the PSI versions went lower than the CUP. Most full power bottleneck rifle cartridges like 30-06 and 308 were in that 50,000-52,000 CUP range, and went up to 60,000-65,000 PSI, yet ammo is reasonably comparable from old to new. I mean, why wouldn't they be? SAMMI didn't just pick the new PSI numbers out of thin air.
Last edited by megasupermagnum; 04-05-2023 at 10:40 PM.
Isn't SAAMI 28,000 CUP AND 28,000 PSI.for the 45/70?
How did that happen?
That is the one time they are the same. I don't know it this is correct but I have read that when using the CUP method the copper crusher cylinder compression is not linear so that is why there is no direct correlation.
PTG still sell the copper crusher cylinders so some are still using them.
https://pacifictoolandgauge.com/677-...sher-cylinders
Last edited by M-Tecs; 04-05-2023 at 11:10 PM.
2nd Amendment of the U.S. Constitution. - "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
"Before you argue with someone, ask yourself, is that person even mentally mature enough to grasp the concept of different perspectives? Because if not, there’s absolutely no point."
– Amber Veal
"The Highest form of ignorance is when your reject something you don't know anything about".
- Wayne Dyer
Pressures for 45/70 is a rabbit hole I want nothing to do with.
That is what makes it interesting.
Lots of data out there.
It's not the data. 45/70 may as well not even have a standard. There's some 45/70's that can't handle 28,000 PSI. Lots of factory ammo is over 28,000 PSI. 45/70 can be 18,000 PSI to 45,000 PSI, there's no real standard.
Didn't say anything about a standard. Just that it is interesting and has plenty of data.
Which it what makes it interesting to me.
The SAAMI standard is 28,000 CUP/PSI. That is considered safe for all 45/70 chambering. Lyman opted to use 18,000 as a recommendation. SAAMI sets the standard for the weakest firearm in normal usage. Lots of firearms are chambered is older lower pressure cartridges that people go well been SAAMI recommendations. The 45 Colt it one example.
https://www.gunsandammo.com/editoria...testing/458750
https://www.shootingsoftware.com/ftp/psicuparticle2.pdf
Last edited by M-Tecs; 04-08-2023 at 08:11 PM.
2nd Amendment of the U.S. Constitution. - "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
"Before you argue with someone, ask yourself, is that person even mentally mature enough to grasp the concept of different perspectives? Because if not, there’s absolutely no point."
– Amber Veal
"The Highest form of ignorance is when your reject something you don't know anything about".
- Wayne Dyer
SAAMI did not pick the new numbers out of thin air. The "new" pressure measuring systems became industry standards which is what SAAMI is all about; industry standards.
Outpost75, as usual, gives an excellent explanation as does megasupermagnum. There is no correlation between CUPs and psi's regardless of the attempts to come up with one. We can't say specifically that 50,000 CUP equals 60,000 psi either because the difference will depend on the cartridge used and the load characteristics.
At lower pressures the CUP is many times higher than psi. However, as the MAP pressure measured gets higher they overlap in the 28,000 +/- range [the 45-70 MAP sits almost squarely at that point]. I have measured the psi of many older loads that were said to be in the 40 - 45,000 CUP range. They were in the 30 - 36,000 psi range. I also have measured the psi of numerous old rounds of factory 357 that were loaded in the late '60s and early '70s. None of them gave a MAP over 30,000. Did the factories dumb down the 357? Your guess is as good as mine.
But keep in mind factories do not load ammo to SAAMI MAP. They load their factory ammo to velocity specifications which a very large +/- factor and to a certain accuracy spec all while keeping the MAP, and in particular, the MPSM under the SAAMI specification for the cartridge. When shooting US made factory ammunition you can expect the psi to be under the SAAMI MAP, sometimes, well under the MAP.
Larry Gibson
“Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
― Nikola Tesla
Posting Permissions
| BP | Bronze Point | IMR | Improved Military Rifle | PTD | Pointed |
| BR | Bench Rest | M | Magnum | RN | Round Nose |
| BT | Boat Tail | PL | Power-Lokt | SP | Soft Point |
| C | Compressed Charge | PR | Primer | SPCL | Soft Point "Core-Lokt" |
| HP | Hollow Point | PSPCL | Pointed Soft Point "Core Lokt" | C.O.L. | Cartridge Overall Length |
| PSP | Pointed Soft Point | Spz | Spitzer Point | SBT | Spitzer Boat Tail |
| LRN | Lead Round Nose | LWC | Lead Wad Cutter | LSWC | Lead Semi Wad Cutter |
| GC | Gas Check |
Reply With Quote